1. Field of the Invention
This invention relates to telephone answering devices and more particularly to a telephone system where multiple answering telephone devices can be used on a single telephone line.
2. Description of the Prior Art
Telephone answering devices are well known in the art and have been used for many years. A typical telephone answering device, also known as a TAD, consists of a prerecorded outgoing message tape and an incoming caller message tape. Recently, telephone systems have been developed allowing the caller to input touch tones to have their calls directed to different recordings or personnel, or to perform different TAD functions such as to play back recorded messages from prior callers over the telephone line.
In U.S. Pat. No. 4,625,079 to Castro, issued on Nov. 25, 1986, circuitry is disclosed for the selective switching of certain devices, including a telephone answering device, by the caller. The Castro device includes a synthetic voice greeting by which a caller may be directed to input a code in order to activate different devices, including a message recording device. However, the Castro device does not employ a standard TAD, such as currently used by millions of households, as the responding unit, but employs a specific synthetic voice activation unit that directs the caller to enter a code to have a message recorded by a separate caller recording unit. The caller, if aware of the access codes of other devices, enters the access code to control such other device, such as the lights. The Castro system is not capable of using a preexisting TAD already owned by the owner of the system.
Further, the Castro device is complicated for a caller to use. Typically, a caller expects to hear a prerecorded message telling the caller to leave a message. In the Castro device, if the caller does not enter the requested code, no message will be recorded.
In the patent to Eswaran, U.S. Pat. No. 4,847,889, issued Jul. 11, 1989, a telephone answering device is disclosed that can have plural outgoing and incoming messages on a single telephone answering device. Different messages are not stored or recorded on separate TADs.
Other patents have also been reviewed. These include: Jackson's PHONE-LINE-LINKED, TONE-OPERATED CONTROL DEVICE, U.S. Pat. No. 4,596,900, issued on Jun. 24, 1986; and Hood et al.'s v/VOICE MAIL SYSTEM ON MAGNETIC TAPE, U.S. Pat. No. 4,747,126, issued May 24, 1988. Both of these inventions also rely on complex circuitry in order to achieve the ends of message direction.
Previously, if a number of TADs had been connected to a single telephone line, there would have been great confusion as all the TADs on the same line would pick up the ringing signal, deliver their messages at the same time, and then all the TADs would record the caller's message. Not only would the cacophony of several outgoing messages have to be endured by the caller, but there would be no privacy regarding the message the caller left. Each TAD on the line would have all the messages and the owner/user of each TAD would know what all the other messages were. This arrangement is obviously not satisfactory.
There exist situations where it would be convenient or necessary to have more than one telephone answering device on a single telephone line. Even in the smallest household, there is a significant demand for at least some privacy. Parents especially recognize this for their children. Roommates also benefit from the respect of the other's privacy. The same is true with business persons of perhaps different trades or professions sharing the same office space.
The problem of having multiple TADs is solved by having multiple telephone lines. However, this is not a convenient or economical solution. The need for a separate TAD may be temporary, or would not justify the expense of a second telephone line. It would also be desirable to be able to use existing TADs thereby greatly reducing both the cost of having multiple TADs and the cost of achieving the overall effect of the system.
The prior art has not addressed this situation in an inexpensive and simple manner. As disclosed herein, the present invention provides simple and inexpensive means by which a plurality of TADs may be used on a single telephone line, where messages may be left on only one telephone answering device connected to a single telephone line shared by many telephone answering devices. Further, existing TADs may be used in the system and no rewiring or reconfiguration is required, save the availability of telephone jacks.